const byte dangerLedPin = 8;
const byte warningLedPin = 9;

#define PIN_PROXIMITY_TRIGGER 3
#define PIN_PROXIMITY_ECHO 7
#define PIN_BUZZER 4
void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);

  pinMode(dangerLedPin, OUTPUT);
  digitalWrite(dangerLedPin, LOW);
  pinMode(warningLedPin, OUTPUT);
  digitalWrite(warningLedPin, LOW);
  pinMode(PIN_PROXIMITY_TRIGGER, OUTPUT);
  pinMode(PIN_PROXIMITY_ECHO, INPUT);
  digitalWrite(PIN_PROXIMITY_TRIGGER, LOW);
  pinMode(PIN_BUZZER, OUTPUT);

}

int measureProximityDistance() {
  // Start a new measurement:
  digitalWrite(PIN_PROXIMITY_TRIGGER, HIGH);
  delayMicroseconds(10);
  digitalWrite(PIN_PROXIMITY_TRIGGER, LOW);

  // Read the result:
  int duration = pulseIn(PIN_PROXIMITY_ECHO, HIGH);
  int distance = duration / 58;
  Serial.print("Distance in CM: ");
  Serial.println(distance );
  return distance;
}

void loop() {
  // put your main code here, to run repeatedly:
  while (true) {
    int distance = measureProximityDistance();
    if (distance < 150) {
      digitalWrite(warningLedPin, HIGH);
      if (distance < 100) {
        tone(PIN_BUZZER, 262, 90);
        digitalWrite(dangerLedPin, HIGH);
      } else {
        digitalWrite(dangerLedPin, LOW);
      }
    } else {
      digitalWrite(warningLedPin, LOW);
    }
    delay(100 );


  }
}